Arc-out shut off valve assembly for a high voltage bushing

ABSTRACT

A high voltage cable termination bushing for terminating a high voltage cable and including a housing having an axial passage, an electrically conductive receptacle within the passage and supported intermediate the ends thereof, the passage being closed at the inner end, and a gas trap valve provided between the inner end of the passage and the receptacle, the valve being biased into engagement with the receptacle that traps gases within the passage. The gas trap valve is opened by the arc-extinguishing rod provided on the conductive probe of the cable connector and having a length sufficient to allow the valve to close at the anticipated position of the probe, with respect to the receptacle where the arc will be extinguished.

United States Patent [191 I FOR A-HIGH VOLTAGE BUSHING lnventorzClarence B. Burns, Oconomowoc,

Wis.

Assignee: RTE Corporation, Waukesha, Wis. Filed: Aug. 21, 1974 Appl.No.: 499,325

References Cited UNITED STATES PATENTS 5/1968 Phillips 339/111 [1113,920,307 Burns Nov. 18, 1975 ARC-OUT SHUT OFF VALVE ASSEMBLY PrimaryExaminer-Roy Lake Assistant Examiner-DeWalden W. Jones Attorney, Agent,or Firm-Ronald E. Barry [57] ABSTRACT A high voltage cable terminationbushing for terminating a high voltage cable and including a housinghaving an axial passage, an electrically conductive receptacle withinthe passage and supported intermediate the ends thereof, the passagebeing closed at the inner end, and a gas trap valve provided between theinner end of the passage and the receptacle, the valve being biased intoengagement with the receptacle that traps gases within the passage. Thegas trap valve is opened by the arc-extinguishing rod provided on theconductive probe of the cable connector and having a length sufficientto allow the valve to close at the anticipated position of the probe,with respect to the receptacle where the arc will be extinguished.

l2 Claim, 3 [Moving Figures probe has HIGH VOLTAGEBUSHING BACKGROUND OTHE INVENTION a bushing which is used totra'p gases after a load breakoperation has been completed and as the probe is withdrawn from theentrance of the'bushing. The valve preventsionized gases 'frombeing'expelled from the bushing into "the atmosphere on separation;Prevention of theexp ulsion of the gases reduces the possibility ofrestrikeeither internally or externally from the probe to the' femalecontact or to the ground shield after the been completely withdrawn fromthe bush- SUMMARY. OF THE INVENTION In the present invention the valveis located internally of the arc chamber sothat the valve does notutilize arc extinguishing space. With the internal valve the arc has nochance of playing on the surface of the gas sealing surfaces, thusgiving a more reliable seal.

. DRAWINGS The bushing'10 of the present invention is used toelectricallyiconnect the conductive probe or contact 12 of an electricalconnector'14 to an electrical apparatus mounted within a housing 16. Ahigh voltage electrical connector ofthis type is shown in US. Pat. No.3,474,386 of Edwin A. Link entitled Electrical Connector and issued onOct. 21,1969. In this type of an electrical connector, a gas evolving,arc-quenching ex-' tension or rod 18 is provided on theend of the probe12. The probe 12 and rod 18 are supported within a housing 20 that isdesigned to matingly engage the bushing 10. The bushing is provided withan electrically conductive receptacle 22 which is designed toelectrically engage the probe 12 and an arc-quenching sleeve 24 whichcooperates with the rod 18 to produce an arc-quenching gas on close-inor interruption. The

arc-quenching materials can be any of the well-known materials used forthis purpose such as hard vulcanized fiber, the acrylics orpolytetrafluoroethylene.

In a high voltage terminator of this type, the gas evolving materialsrespond to the heat of the arc to produce large volumes of gas thatoperate to quickly snuff the arc. It is generally agreed that the arcsnuffing materials produce the intended result. However, as a re- .sultof the confinement of these gases within the bushing, the large volumesof hot ionized gases will be expelled from the bushing on withdrawal ofthe rod from the bushing forming a low resistance electrical pathbetween '-the ground 'shieldand one of the energized contacts, of theseparated electrically conductive members.-lThis condition can beextremely dangerous under fault current conditions increasing the riskof injury to 5 the operator and creating a destructive condition.

. In accordance with the-invention, the bushing 10 is provided with agas trap valve assembly 26 which is located in a position to minimizethe amount of gases expelled on withdrawal of the probe from thebushing. More particularly, the bushing 10 includes a housing 28 formedor molded from a dielectric material and having an axially extendingpassage 30. The housing 28 is adapted to be mounted in an opening 32 inthe enclosure or housing 16 to provide an electrical connection betweena high voltage cable andelectrical apparatus within the housing.

The electrically conductive receptacle 22 is supported within thepassage 30 intermediate the ends thereof by means of a hollow tube orconductive member 34. In this re regard, the conductive member 34 isclosed at the inner end by means of an electrically conductive plug 36having a threaded member 38 extending into the housing 16 for connectionto the electrical apparatus. A reduced diameter threaded section 40 isprovided intermediate the ends of the member 34 for threadedly receivingthe threaded ductive receptacle 22.

The entrance to the passage 30 is lined by-means of end 42 of the conthearc-extinguishing sleeve 24 and extends inwardly into the tubular member34 far enough to engage theend of the conductive receptacle 22. Thesleeve 24 is supportedwithin the tubular member 34 by means of athreaded section 44 provided on the sleeve 24 which is threadedlyreceived on the threaded end 46 of the tubular member 34.

Means are provided at the end of the sleeve 24 for sealingly engagingthe probe -12,and rodl8. Such means is in the form of an O-ring seal 54provided in a groove at the end of the sleeve-24.

The gas produced by the arc on interruption is trapped within the tubeor member 34v by means of the valve assembly 26. The valve assembly 26includes a,

valve member or element 48 which is biased by means of a spring 50 intoengagement with a valve seat 52 provided on the end of the conductivereceptacle 22. It should be noted that the valve assembly 26 is locatedapproximately midway between the ends of the passage 30 so that any gasunder pressure trapped between the valve means 26 and the end plug 36will be prevented from being expelled from the bushing on withdrawal ofthe connector from the bushing. J

In operation, and referring to FIG. 1, the connector 14 is shown mountedon the bushing 10 with the con-.1 ductive probe 12 in electricalengagement with the conductive receptacle 22. The rod 18 extends throughthe receptacle 22 forcing the valve member 48 into the tubular member34'and against the bias of the spring 50. The tubular member 34 willthen be open throughout its full length. v

On withdrawal of the connector 14 from the bushing 10, as seen in FIG.2, the probe 12 and rod 18 will be pulled outwardly from the receptacle22; In the position shown'in FIG. 2, the arc length'between the probe 12and the receptacle 22 will be at approximately the length at which thearc will be extinguished by the gases produced by the heat of the arc.It should also be noted that at this point, the valve member 48 will besimultaneously seated on the valve seat 52 trapping the gases within themember 34. At the instant just prio'rto seating the valve member 48 onthe valve seat 52,g'aspre ssure within the tubular member 34: will 'beequ'al throughout the length of thebushingOn arc interrupatthe end ofthe sleeve 24 and the gas trap valve 26. The majority of the highpressure gases are therefore trapped within the sleeve 34 by the valve26. This reduction in the volume of gases expelled from the bushcontactson circuit disconnectiom FIG. 3 The valve'member or element 60 shown inFIG. 3

provides a means'for delaying closing of the tube 34 for differentvoltage ratings. in this regard, it should be noted that as the arclength or distance increases at higher voltages, the time for closing ofthe tube 34 is delayed in order to trapa greater amount of the gases [inthe tube 34. Such means is in the form of the valve member which isnormally biased by the spring 50 into engagement with the valve seat 52to close the tube 34. The valve member 60 is provided with an extension62 that is axially aligned with the rod 18. The combined length of theextension 62 and the length of the rod 18 are selectedto correspond tothe arc distance for each voltage rating in accordance with the arcingdistance. If the lengths are properly selected, the valve member willclose,,the passage 34 at arc-out.

I claim: t t

l. A high voltage cable termination bushing for connecting an electricalapparatus to an electrically conductive probe having an arcextinguishing rod on the end, said bushing comprising: a housing formedfrom an insulating material and having a passage, said housing beingadapted to be mounted in the entrance to a housing for an electricalapparatus, an electrically conductive member supported within saidpassage intering reduces the-danger of strike over between the livermediate the ends thereof, electrically conductive means closing one endof said passage, said conductive means being electrically connected tosaid conductive member for connecting said bushing to the apparatuswithin the housing, valve means positioned within said passage betweensaid conductive member and said conductive means for trapping gasesbetween said member and said conductive means, said valve means beingnormally in a closed position and opened by the arc exting'uishing rodon the end of the probe on cable termination, on withdrawal of the probethe valve means will close to prevent the escape of gases trapped in thepassage.

2. The bushing according to claim 1 wherein said valve means includes avalve member and a spring positioned to bias said valve member intoengagement with said conductive member to close the passage.

3. The bushing according to claim 2 wherein said valve member includesan extension positioned to engage the rod, said extension and rod havinga combined length established by the voltage rating for the bushing toclose the passage at arc-out.

4 I 4. The bushing according to claim 1 including an arc extinguishingsleeve positioned at-the open end of said passage and an O-ring seal inthe sleeve to sealingly en- I gage the probe.

5. The combination of an electrical connector having an electricallyconductive probeand an arc extinguishing rod on the end of said probeand a high voltage cable termination bushing having a housing fonnedfrom an insulating material and a passage extending through the lengthof the housing, said passage being closed at one end, an electricallyconductive receptacle mounted in said passage intermediate to the endsthereof and being adapted to be electrically connected to an electricalapparatus, said receptacle includinga valve seat at the inner end, valvemeans positioned within said passage between the receptacle and saidclosed end of said passage for movement into engagement with said valveseat to trap gases within said passage, said rod having a lengthsufficient to provide for the extinction of the arc produced onwithdrawal of the probe from the receptacle and to substantiallysimultaneously closesaid valve means at arc out.

6. The combination according to claim 5 wherein I said valve meansincludes a valve member positioned for movement into engagement withsaid valve seat and a spring biasing said valve member into engagementwith said valve seat. 3

7. The combination according to claim 5 including means at the other endof said passage forsealingly engaging said probe and rod. v

8. The combination according to claim 5 including means on said valvemember for' delaying closing of the pa 9. A high voltage cabletermination bushing for connecting an electrical apparatus to anelectrically conductive probe having an arc extinguishing rod .on theend, said bushing comprising: a housing formed from a dielectricinsulating material and adapted to be mounted in the opening of anenclosure for an electrical apparatus, a passage in said housing, ahollow cylindrical electrically conductive tube in said passage, a

' conductive plug closing one end of said tube and being.

adapted to be connected to an electrical device apparatus within theenclosure, an electrically conductive receptacle supported in said tubeintermediate the ends of said housing, normally closed valve meansmounted in said tube for movement into engagement with said receptacleto define a gas trap chamber in said tube, said valve means being openedby the rod on said probe on cable termination, the rod being ofsufficient length to allow the valve means to close onwithdrawal of theprobe from the receptacle a sufficient distance to extinguish the arc.

10. The bushing according to claim 9 including an arc extinguishingsleeve supported at the entrance to said tube and means at the entranceto said sleeve for sealingly engaging said probe and rod.

11. The bushing according to claim 9 wherein said valve means includes avalve element and a spring positioned in said tube to bias said elementinto engagement with said receptacle. 6

12. The bushing according to claim 1 wherein said valve means includesmeans for delaying the closing of said valve means to correspond witharc out.

1. A high voltage cable termination bushing for connecting an electricalapparatus to an electrically conductive probe having an arcextinguishing rod on the end, said bushing comprising: a housing formedfrom an insulating material and having a passage, said housing beingadapted to be mounted in the entrance to a housing for an electricalapparatus, an electrically conductive member supported within saidpassage intermediate the ends thereof, electrically conductive meansclosing one end of said passage, said conductive means beingelectrically connected to said conductive member for connecting saidbushing to the apparatus within the housing, valve means positionedwithin said passage between said conductive member and said conductivemeans for trapping gases between said member and said conductive means,said valve means being normally in a closed position and opened by thearc extinguishing rod on the end of the probe on cable termination, onwithdrawal of the probe the valve means will close to prevent the escapeof gases trapped in the passage.
 2. The bushing according to claim 1wherein said valve means includes a valve member and a spring positionedto bias said valve member into engagement with said conductive member toclose the passage.
 3. The bushing according to claim 2 wherein saidvalve member includes an extension positioned to engage the rod, saidextension and rod having a combined length established by the voltagerating for the bushing to close the passage at arc-out.
 4. The bushingaccording to claim 1 including an arc extinguishing sleeve positioned atthe open end of said passage and an O-ring seal in the sleeve tosealingly engage the probe.
 5. The combination of an electricalconnector having an electrically conductive probe and an arcextinguishing rod on the end of said probe and a high voltage cabletermination bushing having a housing formed from an insulating materialand a passage extending through the length of the housing, said passagebeing closed at one end, an electrically conductive receptacle mountedin said passage intermediate to the ends thereof and being adapted to beelectrically connected to an electrical apparatus, said receptacleincluding a valve seat at the inner end, valve means positioned withinsaid passage between the receptacle and said closed end of said passagefor movement into engagement with said valve seat to trap gases withinsaid passage, said rod having a length sufficient to provide for theextinction of the arc produced on withdrawal of the probe from thereceptacle and to substantially simultaneously close said valve means atarc out.
 6. The combination according to claim 5 wherein said valvemeans includes a valve member positioned for movement into engagementwith said valve seat and a spring biasing said valve member intoengagement with said valve seat.
 7. The combination according to claim 5including means at the other end of said passage for sealingly engagingsaid probe and rod.
 8. The combination according to claim 5 includingmeans on said valve member for delaying closing of the passage.
 9. Ahigh voltage cable termination bushing for connecting an electricalapparatus to an electrically conductive probe having an arcextinguishing rod on the end, said bushing comprising: a housing formedfrom a dielectric insulating material and adapted to be mounted in theopening of an enclosure for an electrical apparatus, a passage in saidhousing, a hollow cylindrical electrically conductive tube in saidpassage, a conductive plug closing one end of said tube and beingadapted to be connected to an electrical device apparatus within theenclosure, an electrically conductive receptacle supported in said tubeintermediate the ends of said housing, normally closed valve meansmounted in said tube for movement into engagement with said receptacleto define a gas trap chamber in said tube, said valve means being openedby the rod on said probe on cable termination, the rod being ofsufficient length to allow the valve means to close on withdrawal of theprobe from the receptacle a sufficient distance to extinguish the arc.10. The bushing according to claim 9 including an arc extinguishingsleeve supported at the entrance to said tube and means at the entranceto said sleeve for sealingly engaging said probe and rod.
 11. Thebushing according to claim 9 wherein said valve means includes a valveelement and a spring positioned in said tube to bias said element intoengagement with said receptacle.
 12. The bushing according to claim 1wherein said valve means includes means for delaying the closing of saidvalve means to correspond with arc out.